The Lord is impartial : we can understand that if we are not envious

In SB 7.1.1 King Pariksit asks Suta Goswami as to why the Lord became partial towards Indra and helped him kill his enemies(Hiranyaksa, Hiranyakasipu, Vrtrasura, etc). Since the Lord says that He is suhrda-sarva-bhutanam [Bg. 5.29], the well-wisher of all living entities, how could He act with partiality by killing demons?

To this Sukadeva Goswami replies (from purport to 7.1.8)"The Supreme Personality of Godhead is not partial to anyone. Everyone works under the influence of various modes of material nature, and when the various modes are prominent, the demigods or demons appear victorious under the influence of these modes." Also because we are covered we cannot fathom the activities of the Lord and consider Him to be partial.

And then Sukadeva Goswami finally says in SB7.1.9 "The all-pervading Personality of Godhead exists within the heart of every living being, and an expert thinker can perceive how He is present there to a large or small extent. Just as one can understand the supply of fire in wood, the water in a waterpot, or the sky within a pot, one can understand whether a living entity is a demon or a demigod by understanding that living entity's devotional performances. A thoughtful man can understand how much a person is favored by the Supreme Lord by seeing his actions."

The essence is the Lord is not partial, He is equally available to everyone.His favor on us depends on our receptivity. As Srila Prabhupada explains this very nicely in his purport : "A teacher instructs the student if the student is capable of taking more and more instructions. Otherwise, in spite of being instructed by the teacher, the student cannot make strides in his understanding. This has nothing to do with partiality. When Krsna says tesam satata-yuktanam bhajatam priti-purvakam/ dadami buddhi-yogam tam, this indicates that Krsna is prepared to give bhakti-yoga to everyone, but one must be capable of receiving it. That is the secret. Thus when a person exhibits wonderful devotional activities, a thoughtful man understands that Krsna has been more favorable to this devotee.

Non-Enviousness
Thus devotees must be non-envious and must understand that Krsna has bestowed His favor upon a devotee owing to his advanced position and because of that Krsna does not become partial. We must not become envious and try to minimize the devotee's activities.

A Vaishnava should thus be nirmatsara - non envious and must appreciate the service rendered to the Lord by other devotees.

Srila Prabhupada further elaborates with an analogy:

"Krsna is equal to everyone, and according to one's ability to receive the favor of Krsna, one advances in Krsna consciousness. Srila Vishwanatha Cakravarti Thakura gives a practical example in this connection. In the sky there are many luminaries. At night, even in darkness, the moon is extremely brilliant and can be directly perceived. The sun is also extremely brilliant. When covered by clouds, however, these luminaries are not distinctly visible. Similarly, the more one advances in sattva-guna, the more his brilliance is exhibited by devotional service, but the more one is covered by rajo-guna and tamo-guna, the less visible his brilliance, for he is covered by these qualities. The visibility of one's qualities does not depend on the partiality of the Supreme Personality of Godhead; it is due to various coverings in different proportions. Thus one can understand how far he has advanced in terms of sattva-guna and how much he is covered by rajo-guna and tamo-guna."